Position indicators have been known for a long time, these are devices apt to detect the instant displacement of an element, or member, of an industrial operating machine during the adjustment thereof. This type of device is normally associated with an actuation shaft of the machine element and makes a number visible—and due to this it is called also numerator—indicating the position reached by the machine element depending on the revolution number and on the revolution fractions of said shaft. Thereby, acting on different control shafts, the operator is able to set up in the correct position, by suitably adjusting the different elements making up the machine for the process it is to carry out.
The actuation shaft of this type of device is usually engaged with a suitable bush seat, freely rotating in the position indicator support, and associated with a motion transmission so as to transmit the motion to measuring means and means for viewing the displacement that has taken place.
Typically, this type of device can be based on a mechanical or digital measurement. In the case of digital level indicators, it is necessary to provide an electric supply, and therefore to actuate the safety rules for guaranteeing protection of the operators and of the machine. For such purpose, the ruling bodies, such as the Comitato Elettrotecnico Italiano (CEI, Italian Electrotechnical Committee), have defined a classification for indicating in short the protection level of an electric apparatus from accidental or intentional contact with a human body or with objects, and the protection from water contact, reported in the jargon as IP Classification.
The manufacturers of electric and electronic machines are continuously looking for devices which are able to meet the strict properties of the highest degrees of the IP classification, therefore improving their equipment with special devices.
In particular, however, the Applicant could detect that known-art position indicators are unable to simultaneously provide full protection from dust and protection from temporary immersion, properties indicated in the classification by wording in International Protection Code 67 (IP67).
However, it is understood that these properties have a fundamental strategic importance for a special type of processing, for which it is necessary to work simultaneously with significant amounts of dust in the presence of liquid substances (think of certain types of cutting systems, in which precise measurement is a fundamental element).